This invention relates to control mechanisms for motor vehicle engine operation and more particularly to systems for regulating the speed of the motor vehicle. The device is particularly useful for controlling the operating speed of diesel engine powered motor vehicles at a preset value.
A speed control system or cruise control regulates the speed of a vehicle at a preset level which is determined by the operator based on the vehicle load, road conditions, and other factors. Speed control is typically accomplished by a fuel bypass, throttle linkage control means or engine oil pressure control means.
Cruise control systems are being used with increased frequency in the trucking industry by fleet owners and owner-operators for reasons of economy, comfort and safety. Automatic speed control reduces the amount of fuel consumption during vehicle operation. Speed control also minimizes overall vehicle maintenance and particularly that required by the engine. Further, speed control increases vehicle operating safety through improved adherence to posted speed limits. This is a particularly important result for buses and motor coaches. Additionally, through adherence to posted speed limits, speed control systems help to maintain good operator driving records. Finally, speed control systems provide added operator comfort and convenience through automatic maintenance of a preset speed.
Ideally, the speed control should accurately maintain the set speed without appreciable surge, overshoot and droop. The device should provide such speed maintenance in a fast, smooth and substantially imperceptable fashion. The device should also provide a safety disconnection mechanism during braking, gear shifting and in the event of a power failure or other system failure. Finally, the speed control device should have a compact and simple design so that it is easy to manufacture and install.
In the past, cruise control devices have been used and proposed to regulate the speed of motor vehicles, and some of the prior art devices are usable for diesel powered vehicles, including trucks. However, these devices are generally complex, difficult to construct and install, and are inefficient and often unsafe to use. Specifically, some prior art devices employ pneumatic systems utilizing either positive air pressure or a vacuum to control an actuator which is operative on a carburetor or fuel pump. These pneumatic systems are complex, difficult to install and often very expensive.
Some prior art devices are ineffective at maintaining the preset speed, particularly under windy weather conditions. These devices surge to maintain vehicle speed under windy conditions. Surge may also be caused by heavy loads, steep grades or fast acceleration. The surge phenomenon is both uncomfortable for the operator and unsafe. Other prior art devices provide slow, rough and inaccurate speed control which results in disconcerting speed variations. Such variations lead to operator dissatisfaction and rejection.
Other prior art devices are unsafe in that they do not provide a reliable, safety mechanism for disengagement of the speed control system upon deactivation by the driver, vehicle braking, gear shifting, electrical system failure and other emergencies.
Despite the need for a cruise control device in the art which provides efficient and reliable speed regulation for motor vehicles, particularly diesel powered vehicles, which is simple to manufacture, install and use, and which overcomes the limitations and problems of the prior art, none insofar as is known has been proposed or developed.
Accordingly, it is an object of the present invention to provide a speed control device which provides safe, reliable vehicle speed control under a variety of weather, load grade and acceleration conditions. It is a further object of the present invention to provide a speed control device which minimizes vehicle surge, particularly in high wind conditions. It is another object of this invention to provide a device which yields fast, smooth and substantially imperceptible speed control. Also, it is an object of this invention to provide a speed control system which is compact, unitary, uncomplicated, and which is easy to manufacture, install and maintain.